Western Madagascar



ID


579

Author(s)


John S. Sparks, Department of Ichthyology, Division of Vertebrate Zoology, American Museum of Natural History, New York, NY, USA


Countries


Madagascar

Major Habitat Type


Xeric freshwaters and endorheic (closed) basins

Drainages flowing into


Indian Ocean


Description

Boundaries

This ecoregion includes the basins of the Manambolo, Tsiribihina, Mangoky, and Onilahy rivers in western Madagascar. 

Freshwater habitats

Western rivers are long, generally slow flowing, and subject to seasonal fluctuations in water level and flow. Tidal influence is significant in the lower reaches of these watercourses (Kiener & Richard-Vindard 1972). Many of western Madagascar’s smaller river basins are dry from April to November (Aldegheri 1972).

Distinctive freshwater habitats within this region include tsingy or karst  formations characterized by fissures, subterranean streams, sinkholes, and caverns produced by erosion, located along the western coast and isolated larger rivers in the central highlands with distinct assemblages of fish species. Lac Itasy, located to the east of the capital Antananarivo in the western central highlands, once supported a diverse assemblage of native fishes, although exotics have almost entirely replaced the native species.

Terrestrial habitats

Deciduous forest is present in the wetter parts of this ecoregion, but drought-tolerant vegetation, such as Didiereaceae and Euphorbia thickets, dominates the landscape (Lowry et al. 1997). 

Justification for delineation

This ecoregion is defined by those basins in western Madagascar with an annual average of less than 1400 mm of rain (Food and Agriculture Organization & International Institute for Applied Systems Analysis 2000). Compared to the wetter northwestern basins, the dry western basins are substantially more influenced by vast seasonal fluctuations in flow rate that could easily wipe out existing fish populations during periods of complete desiccation.

Level of taxonomic exploration

Poor. To date a comprehensive ichthyological survey of the western basins has not been completed and thus comprehensive data are lacking. Many of the western basins are extremely difficult to access, as roads are few and in poor condition.


References

  • Aldegheri, M. (1972). "Rivers and streams on Madagascar" Battistini, R.;Richard-Vindard, G. ( (Vol. Biogeography and ecology in Madagascar, pp. Dr. W. Junk ) 261-310.
  • Brenon, P. (1972). "The geology of Madagascar" R. Battistini and G. Richard-Vindard (Ed.) Biogeography and ecology in Madagascar ( pp. 27-86 ) The Hague, The Netherlands: Dr. W. Junk.
  • Donque, G. (1972). "The climatology of Madagascar" R. Battistini and G. Richard-Vindard (Ed.) Biogeography and ecology in Madagascar ( pp. 87-144 ) The Hague, The Netherlands: Dr. W. Junk.
  • Food and Agriculture, O. and International Institute for Applied Systems, A. (2000) \Global Agro-Ecological Zones - 2000\ (2003)
  • Glaw, F.;Vences, M. (1994). "A field guide to the amphibians and reptiles of Madagascar" Leverkusen, Germany: Moos-Druck.
  • Kiener, A. (1963). "Poissons, peche et pisciculture a Madagascar" Publ. Centre Technique Forestier Tropical 24 (1-224)
  • Kiener, A. and Richard-Vindard, G. (1972). "Fishes of the continental waters of Madagascar" R. Battistini and G. Richard-Vindard (Ed.) Biogeography and ecology in Madagascar ( pp. 477-499 ) The Hague, The Netherlands: Dr. W. Junk.
  • Kuchling, G. (1988). "Population structure, reproductive potential, and increasing exploitation of the freshwater turtle Erymnochelys madagascariensis" Biological Conservation 43 pp. 107-113.
  • Langrand, O. (1990). "Guide to the birds of Madagascar" New Haven, Connecticut, USA: Yale University Press.
  • Lowry, P. P., II, Schatz, G. E. and Phillipson, P. B. (1997). "The classification of natural and anthropogenic vegetation in Madagascar" S. M. Goodman and B. D. Patterson (Ed.) Natural change and human impact in Madagascar ( pp. 92-123 ) Washington, D.C., USA: Smithsonian Institution Press.